It's raining on Saturn, and the rings are responsible

This artist's concept illustrates how charged water particles flow… (NASA/JPL-Caltech/Space…)

Saturn's rings are not just beautiful to look at; it turns out they are also responsible for rain falling on the planet.

Using data collected from the Keck Observatory in Hawaii, scientists found that the amount of "ring rain"--when water particles fall from Saturn's rings onto the planet below--is significantly more than previously thought, and may be responsible for the pattern of dark bands or shadows that appear on the planet's surface.

James O'Donoghue, the lead author on the paper which appeared in Nature and a postgraduate researcher at the University of Leicester in England, told Space.com that about "one Olympic-sized swimming pool of water is falling on Saturn per day."

Ring rain is not like regular rain, of course--the water is not coming over in big gushes or even in droplets.

Instead, O'Donoghue surmised that tiny charged water particles are moving from Saturn's rings--which are made up almost entirely of ice--along magnetic pathways between the rings and the planet. Once they hit Saturn, they neutralize glowing triatomic hydrogen ions in the planet's upper atmosphere.

Those areas where the ions are neutralized appear darker than other parts of the planet in infrared images, leaving "shadows" on Saturn in a pattern that mimics the rings themselves.

"It's like a shadow map of the rings has imprinted itself on the planet," said Kevin Baines of the Jet Propulsion Laboratory in La Canada Flintridge, a coauthor on the paper.

"Saturn is the first planet to show significant interaction between its atmosphere and ring system," O'Donoghue said in a statement. "The main effect of ring rain is that it acts to 'quench' the ionosphere of Saturn, severely reducing the electron densities in regions [where] it falls."

The discovery leads to more scientific questions, especially how ring rain affects the rings. Also: Will the ring rain ultimately lead to the wasting away of Saturn's picturesque rings? And, can further analysis of the rate of ring rain help scientists figure out the age of the rings?

The paper describing the ring rain appeared in the journal Nature this week.